Aviation of World War II

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JRM Mars

Transport Flying Boat


JRM Mars in flight

JRM Mars is a long-range patrol aircraft, a four-engine flying boat, developed in 1938-1943. The development was based on the successful Martin PBM Mariner project, which entered service in 1939.

For its time, the car was outstanding. With a total flight weight of more than 65 tons, the seaplane was supposed to develop a cruising speed of 365 km / h with a range of up to 8 thousand km. With four state-of-the-art Wright R-3350 Duplex Cyclone radial engines, the power plant would develop 8,000 horsepower. The construction of the prototype aircraft began in August 1940, and on September 27, 1941, the aircraft left the assembly shop.

By the time the flight tests were completed, the American fleet was already armed with the Consoldated-Vultee PB2Y Conorado, a four-engine patrol bomber. As a result, the purpose of the Martin Mars flying boat was revised and from a patrol bomber it was retrained into a transport seaplane. All military equipment, including defensive equipment (machine-gun turrets), were removed, and the vehicle's fuselage was rebuilt for the convenience of transporting soldiers and military equipment. As a result, the new version of the seaplane received the designation XPB2M-1R.

Impressed by the characteristics demonstrated by the XPB2M-1R, the US Navy ordered 20 production vehicles from Martin at once, which were assigned the JRM-1 index. At the same time, the serial flying boats differed from the prototype by a large single keel, while the plumage on the XPM2M-1 was two-keel. The changes also included the installation of more powerful 2400 hp R-3350-8 engines on the aircraft, which rotated new four-blade propellers. The rear of the fuselage step was also widened. This was done to improve the handling of the flying boat in the water.

In total, from 1945 to 1947, 1 experimental and 6 serial flying boats of this type were produced. It is worth noting that Martin Mars was the largest seaplane ever mass-produced, surpassing it in size Hughes H-4 Hercules was assembled in a single copy.

JRM-2 Mars Specification
Экипаж 4
Wing span, m 60.96
Wing area, m² 342.15
Length, m 36.65
Height, m 13.59
4×PE Wright R-3350-18 Duplex Cyclone, h.p. 4×2200
Weight, kg:
Empty 34,279
Gross weight 74,843
Maximum speed, km/h 356
Cruising speed, km/h 240
Service ceiling, m 4,450
Service range, km 7,958
Payload, kg 9,300

133 soldiers or 84 stretchers and 25 escorts or 301 passengers or 9300 kg of cargo.

The end of World War II led to an adjustment of the order by the Navy and a total of 6 aircraft were produced, the first of which was lost in August 1945. Despite the small size of the series, even in it the aircraft differed from each other. So, the last seaplane differed from the JRM-1 version by installing more powerful engines, it received four Pratt & Whitney R4360-4T Wasp Major engines with a capacity of 3000 hp each. everyone. The vehicle received the designation JRM-2. Such an aircraft, due to the increased power of the engines, had an increased flight weight of 9072 kg.

Another boat was lost near Honolulu on May 5, 1950. Immediately after takeoff, the plane's engine caught fire. The car was able to land safely, the crew left the seaplane after the fire spread from the engine to the wing fuel tanks. The remaining 4 aircraft served as part of the VR-2 aviation squadron, which was engaged in the transportation of goods and people. The main routes of these aircraft were in the Pacific Ocean. On May 19, 1949, Mars even set a kind of record, transporting 301 people + 7 crew members.

Flying boats were actively used by American naval aviation until 1956, when their service came to an end, but were later used in the timber industry.

The last remaining aircraft, which is also the first to be produced, flew to extinguish fires back in 2013.

Photo Description
Drawing JRM-1 Mars Martin Drawing JRM-1 Mars Martin
JRM Mars Martin in flight JRM Mars Martin in flight


  • "Encyclopedia of military engineering" /Aerospace Publising/
  • "American warplanes of World War II" /under cor. David Donald/